Cellulases/hemicellulases cleave non-starch polysaccharides contained in flour. This affects the water retention and water binding capacity, viscosity, and proofing (rising) capacity of the dough as well as the texture, aroma, taste and freshness of the bead.
Generally speaking, the use of cellulases/hemicellulases gives an improved oven spring to the dough and an improved bread volume, grain structure and anti-staling properties to the finished bakery product. However, the dough may become too slack and stickier, which may cause problems. It is thereby necessary to use dosages too low for an optimum baking result to be achieved, so that the enzymes in question cannot be utilized to the full extent. At low dose levels, cellulases/hemicellulases make the mechanical handling of the dough easier whereas the effect of cellulases/hemicellulases on the process tolerance, for instance, may be insufficient when used alone, wherefore emulsifiers have to be used as additives.
It has been found that the addition of glucose oxidase (GO) and sulfhydryl oxidase (SHX) strengthens the dough. Flour having a low protein content is usually classified as weak. The gluten of weak flour (the extensible, rubbery mass formed when mixing flour with water) is very extensible under stress but does not return to its original dimensions when the stress is removed. Flour with a high protein content is classified as strong. The gluten of strong flour is less extensible than that of weak flour. It is more resistant to mixing.
Strong flour is often preferred for baking purposes, since the rheological and handling properties of a dough prepared from such flour are superior to those obtained with weak flour. In addition, the shape and texture of a bakery product prepared from strong flour are remarkably better as compared with weak flour.
A dough prepared from strong flour is also more stable as compared with that prepared from weak flour. This is one of the most important--if not the most important--properties in view of the baking process.
In addition to those mentioned above, enzymes affecting baking further include amylases and proteases. Amylases produce sugars for yeast food (from damaged starch, for instance). Alpha-amylase breaks down such starch into dextrines which are further broken down by beta-amylases into maltose. Due to this, an increased amount of gas is produced by the yeast, which increases the bread volume. At the same time, the increased formation of dextrines and maltose improves the crust color, aroma and taste of the final product. Furthermore, alpha-amylase retards the chemical ageing of bread (staling of the bread crumb). Proteases, in turn, break down flour proteins, resulting in a more stretchy dough. The dough "matures" more rapidly whereby the need of mixing and the fermentation times of the dough can be decreased; due to the better baking properties, the gas retention of the dough, and the volume and grain structure of the bread are improved.
It has been known for a long time to use so-called bread improvers in the preparation of dough. The function of such bread improvers, including emulsifiers, unspecific oxidants (such as ascorbic acid (dehydroascorbic acid), potassium bromate, peroxides, iodates, etc.) etc., is to form inter-protein bonds which strengthen the dough.
Emulsifiers used in baking have many effects, such as retardation of chemical ageing, strengthening of gluten and an even emulsification of fat through the dough. Conventional emulsifiers used in baking include monoglycerides, diacetyl tartaric acid esters of mono- and diglycerides of fatty acids, and lecithins. Lecithin used in baking is normally obtained from soya. Lecithin may be in many different product forms, such as raw lecithin, de-oiled lecithin, or a carrier spray-dried lecithin, fractionated lecithin, chemically modified and enzymatically modified lecithin. Lecithin is a mixture of different phospholipides, the composition of which is variable. Furthermore, the different product types and commercial products behave in different ways in baking applications. Normally the lecithin content of commercial products is specified as acetone insoluble material (AI). Following commercial product examples from Lucas Meyer, Hamburg, Germany, illustrate the range of products: Emulpur N (de-oiled), phospholipide content min 95%, Lecimulthin M-035 (spray-dried), phospholipide content appr. 28.0%. In addition to its emulsifying effect, lecithin improves the baking properties of the other baking ingredients, increases bread volume, improves anti-staling properties and has a favorable effect on the crumb and crust texture.
Many commonly used bread improvers have disadvantageous effects; in particular, they may have negative organoleptic effects on the final bakery product. On the other hand, the use of bromate, e.g., is not accepted in many countries.
From the consumer's point of view, it is advantageous to minimize the use of the above-mentioned chemical additives.
U.S. Pat. No. 2,783,150 discloses a method of treating flours with glucose oxidase enzyme for improving the dough formation and baking properties. This results in improved dough strength, improved dough handling properties, and improved texture and appearance of the baked product. The use of glucose oxidase in combination with ascorbic acid is recited as particularly advantageous.
Japanese Patent Specification No. 5701/1968 discloses a method of improving the quality of bread by the addition of an enzyme composition containing cellulase and/or hemicellulase to the dough. It is emphasized in the patent specification that the addition of this enzyme composition causes decomposition of insoluble fibrous components contained in flour, such as cellulose and pentosan which as such would considerably deteriorate the quality of bread by rendering the dough non-homogeneous and by preventing the formation of gluten. It is recited that the bread product so obtained has an increased volume, more uniform grain structure and slower ageing during storage.
U.S. Pat. No. 136,003, filed in December 1987, describes the use of an enzyme preparation containing glucose oxidase and microbiological sulfhydryl oxidase for increasing the strength of a dough prepared from flour, water and yeast. Such an enzyme preparation is recited to improve the rheological properties of the dough and, in particular, to improve the stability of the dough.
The combination of glucose oxidase and sulfhydryl oxidase has also been shown to dry the surface of dough, which improves the machinability of the dough.
It has now been unexpectedly found that the combined use of hemicellulase/cellulase and glucose oxidase enzymes, or glucose oxidase and sulfhydryl oxidase enzymes has a complementary synergistic effect, so that the processability and process tolerance, oven spring, volume and texture are clearly better than what could be expected when using each one of these enzymes alone.
The invention relates to a method of improving the rheological properties of flour dough and the properties of the final bakery product by adding to the dough an effective amount of an enzyme preparation containing hemicellulose and/or cellulase and glucose oxidase, or glucose oxidase and sulfhydryl oxidase. By the use of this enzyme composition, a dough prepared from weak flour will have the typical advantageous properties of a dough prepared from strong flour (advantageous rheological properties and "good gluten properties", handling properties and tolerance in a mechanized industrial bread making process) while the final bakery product keeps its desired shape, has good volume, good grain structure and good organoleptic properties. The enzyme composition of the invention can also either partially or fully replace conventional bread improves classified as additives (e.g., emulsifiers). The surface of a dough containing the enzyme preparation of the invention remains dry, which is an important factor in industrial processes.